/Engine/Plugins/FX/Niagara/Source/Niagara/Public/NiagaraUserRedirectionParameterStore.h
If necessary it will replace the supplied variable with the fully qualified namespace (User.) appropriate for a user variable. Will return false if the variable wasn't able to be converted into a valid user namespaced variable.
bool RedirectUserVariable ( [FNiagaraVariableBase](API\Plugins\Niagara\FNiagaraVariableBase) & UserVar ) const